In the field of X-ray photography for medical and industrial purposes, radiation imaging systems using radiation detecting elements in place of X-ray sensitive films are coming to be used widely in recent years. Such a radiation imaging system is highly convenient in that there is no need for development as in the case of X-ray sensitive films and radiation images can be checked in real time, etc., and also provides advantages in terms of data storability and ease of handling.
With a general radiation imaging system, an incident radiation image is converted to visible light, etc. (including ultraviolet rays and infrared rays) by a scintillator, and the converted light image is detected by photodetecting elements arrayed in one dimension or two dimensions and output electrical signals corresponding to image data. In particular, radiation detecting elements of a structure, in which a scintillator is directly deposited onto a photodetecting surface of a solid-state imaging element, provide a merit of being easy to handle.
A solid-state imaging element becomes lower in manufacturing yield as its screen size becomes larger. There is thus a limit to making each individual imaging element large in screen size. Meanwhile, with radiation, because, unlike with visible light, etc., an image cannot be reduced by an optical system, an imaging element of a size that covers real images is required. For example, among chest X-ray photography devices, mammography devices for breast cancer screening, panorama photography devices for jaw portions, etc., there is known an art, in which a large-screen imaging element is formed from a buttable array of small imaging elements aligned in a tile-like manner (see, for example, Patent Document 1).
There is also known an art for reducing dead areas at boundary portions between respective imaging elements in a buttable array by shifting a plurality of detectors to the front and rear as viewed from a direction of incidence of radiation so that imaging regions of the detectors overlap (see, for example, Patent Document 2).
Patent Document 1: Japanese Published Unexamined Patent Application No. H9-153606
Patent Document 2: Japanese Published Unexamined Patent Application No. 2000-292546